JP2002261157A - Electrostatic chuck and treating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrostatic chuck having detachment response and small gas leakage and a treating device using it while the uniform heating and high attraction force of a substrate are maintained. SOLUTION: In the electrostatic chuck provided with a ceramic dielectric layer 2, a mounting face 3 provided on the surface of the ceramic dielectric layer 2 and holding an object to be held, and a holding electrode 4 provided so as to be opposed to the mounting face and the surface of the contrary side, the mounting face 3 is separated into a mounting face outer peripheral area 3b and a mounting face center area 3a by a gas jetting groove 5, surface roughness Ra is 0.6-1.5 μm in the mounting face center area 3a, 0.7 μm or less in the mounting face outer peripheral area 3b, the surface roughness of the mounting face outer peripheral area 3b is smaller than that of the mounting face center area 3a, and the height of the mounting face outer peripheral area 3b is 0.6 μm or higher than that of the mounting face center area 3a.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrostatic chuck, and more particularly, to an electrostatic chuck, which is suitably used for processing, transport, and the like in which a wafer is electrostatically attracted and held in a semiconductor manufacturing process such as etching, CVD, and sputtering. The present invention relates to an electrostatic chuck and a processing device.

[0002]

2. Description of the Related Art In a semiconductor manufacturing apparatus used for manufacturing a semiconductor device including a liquid crystal, it is necessary to hold a substrate such as a wafer in order to process or transport the substrate by film formation, etching or exposure. In particular, an electrostatic chuck that electrostatically holds a substrate can be used in a vacuum or in a corrosive gas atmosphere, and is suitable for manufacturing semiconductors.
It is heavily used.

However, in a plasma processing apparatus that performs processing in a vacuum, the space between the wafer and the surface of the electrostatic chuck on which the wafer is placed is in a vacuum state, and heat transfer between the wafer and the electrostatic chuck deteriorates. Therefore, there is a problem that the wafer is locally heated by the ion irradiation during the plasma processing, the wafer temperature becomes non-uniform, and as a result, a defect occurs.

Therefore, a number of grooves are formed radially from the center of the wafer mounting surface of the electrostatic chuck to the outer peripheral portion, and gas is introduced into the grooves as a medium for heat conduction.
Japanese Patent Laid-Open No. 2-1 has disclosed a method of preventing a temperature rise of a wafer and reducing a temperature variation in a wafer surface.
19131.

In addition, the surface roughness of the wafer mounting surface of the electrostatic chuck is reduced to 0.3 μm or less, the contact area between the wafer and the electrostatic chuck is increased, heat transfer is improved, and the uniformity of the substrate is improved. This has been proposed in JP-A-6-112302.

Further, the wafer mounting surface is separated into a mounting surface central region and a mounting surface outer peripheral region by a gas ejection groove, and the surface roughness of the mounting surface outer peripheral region is smaller than the mounting surface central region. Japanese Patent Application Laid-Open No. 8-55905 discloses an electrostatic chuck in which the temperature uniformity on the wafer surface is improved by setting the surface roughness to 0.2 to 0.5 μm.

[0007]

However, in the electrostatic chuck described in Japanese Patent Application Laid-Open No. 2-119131, a large number of radial grooves are provided from the center. However, since the distance between the grooves is large in the outer peripheral portion and the temperature changes depending on the portion, there is a problem that the heat uniformity is insufficient.

In the electrostatic chuck described in Japanese Patent Application Laid-Open No. 6-112302, the surface roughness of the wafer mounting surface is small, and the uniformity of the substrate is improved. However, there is a problem in that residual adsorption occurs when cutting is performed, the detachment response of the held object is deteriorated, the throughput is reduced, and the productivity is low.

Further, the electrostatic chuck described in Japanese Patent Application Laid-Open No. 8-55905 has a problem that the defect rate is high in addition to the problem of the detachment responsiveness described above. That is, although the temperature uniformity is high because the surface roughness of the electrostatic chuck is small, the wafer warps due to the temperature rise, and gas leaks from the gas ejection grooves provided with gas holes near the outer peripheral edge of the substrate. However, there is a problem that the uniformity and reproducibility of the plasma processing are adversely affected, and the defective rate increases.

[0010] As described above, the conventional electrostatic chuck has not been able to obtain a material excellent in all of the characteristics of heat uniformity, suction force, and detachment response. As a result, the throughput is reduced in the semiconductor manufacturing process, There was a problem of increasing the defect rate.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an electrostatic chuck with less detachment response and less gas leak while maintaining the uniform temperature of the substrate and a high attraction force, and a processing apparatus using the same.

[0012]

SUMMARY OF THE INVENTION The present invention controls the surface roughness and the position (height) of the outer peripheral region of the mounting surface and the central region of the mounting surface to maintain the uniform temperature of the substrate and high suction power. Meanwhile, it is based on the finding that the departure response and gas leak can be improved.

That is, an electrostatic chuck according to the present invention comprises a ceramic dielectric layer, a mounting surface provided on a surface of the ceramic dielectric layer, for holding an object to be held, and an opposite side to the mounting surface. A holding electrode provided so as to face the surface of the surface, the mounting surface is separated into a mounting surface outer peripheral region and a mounting surface central region by a gas ejection groove, and the surface roughness is reduced. The _Ra is 0.6 to 0.6 in the center area of the placement surface described above.
1.5 μm, 0.7 μm or less in the mounting surface outer peripheral region, the surface roughness of the mounting surface outer peripheral region is smaller than the surface roughness of the mounting surface central region, and the mounting surface outer peripheral region. Height is 0.6 higher than the height of the placement surface center area.
It is characterized by being higher than μm.

As described above, the surface roughness R in the center area of the mounting surface
_a is increased to 0.6 to 1.5 μm, and the horizontal level between the mounting surface outer peripheral region and the mounting surface center region is 0.6 μm.
Since the above-described height difference is provided, the gas enters the gap between the object to be held and the central area of the mounting surface, and the heat uniformity can be improved.

Further, even if an object to be held (hereinafter simply referred to as a wafer) such as a wafer is warped due to a rise in temperature due to the formation of the height difference, the deformation is absorbed and the end of the wafer is placed on the mounting surface. And prevents the gas from leaking from the outer peripheral region of the mounting surface. At the same time, the surface roughness of the outer peripheral region of the mounting surface is set to 0.7 μm or less, so that a high suction force is obtained in the outer peripheral region of the mounting surface. be able to.

It has been found that the surface roughness of the mounting surface has a large effect on the attraction force and the residual attraction force, and the outer peripheral region of the mounting surface has a small surface roughness and the central region of the mounting surface has a relatively large surface. By making the surface rough, it was possible to realize sufficient adsorption force and quick desorption response. That is, since the surface roughness is large in the mounting surface center region and small in the mounting surface outer peripheral region,
Although the contact area between the wafer and the electrostatic chuck is reduced, as a result, although a large suction force is exhibited in the outer peripheral area of the mounting surface,
In the central area of the mounting surface, the attraction force is suppressed, and the detachment responsiveness of the held object is improved.

[0017] In particular, the maximum surface roughness R _max of the mounting surface outer peripheral region and the mounting surface central region, is preferably 2μm or less. As a result, local gas leakage can be prevented, and the heat uniformity of the held object, a decrease in the adsorbing power, and the detachment response can be further improved.

Preferably, a distance from a peripheral end of the mounting surface to an outer periphery of the gas ejection groove is 10 mm or less. As a result, the outer peripheral area of the mounting surface can be made narrower, the central area of the mounting surface can be made wider, the area where the gas is uniformly heated by gas can be expanded, and the dead space in the outer peripheral area can be made narrower. The number of chips increased,
Productivity can be improved.

Further, it is preferable that the density of the ceramic dielectric layer is 98% or more and the maximum pore diameter is 2 μm or less. This makes it easy to control the surface roughness of the mounting surface, Particles generated by friction with the processed object can be reduced.

Furthermore, the ceramic dielectric layer 5
Preferably 0 ℃ the volume resistivity is 10 ⁷ ~10 ^{1 2} Ωcm, thereby Johnson small applied voltage -
It is possible to obtain a high adsorption force based on the Rabbeck force.

It is preferable that the ceramic dielectric layer contains aluminum nitride as a main component.
It is resistant to corrosion by corrosive gas or plasma containing fluorine, chlorine, etc., and can extend the product life.

Further, the processing apparatus of the present invention is characterized in that the electrostatic chuck of the present invention is provided in the inside thereof, so that it is possible to increase the productivity and realize the processing at low cost and reliability.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An electrostatic chuck according to the present invention is shown in FIGS.
4 will be described.

Referring to FIG. 1A, an electrostatic chuck 1 according to the present invention comprises a ceramic dielectric layer 2, a mounting surface 3 provided on the surface of the ceramic dielectric layer 2, and a mounting surface. 3 and an electrode 4 provided on the opposite surface. Note that the ceramic dielectric layer 2 is provided so as to be sandwiched between the mounting surface 3 and the electrode 4. Although not shown, it is needless to say that a connection wiring for supplying a voltage to the electrode 4 is included.

The mounting surface 3 is a portion for mounting an object to be held such as a Si wafer, and is divided into a mounting surface central region 3a and a mounting surface outer peripheral region 3b by a gas ejection groove 5. I have. The mounting surface center region 3a corresponds to a part of the mounting surface 3 between the pair of gas ejection grooves 5 in FIG. 1A, and the mounting surface outer peripheral region 3b A portion outside the gas ejection groove 5.

A gas hole 6 is connected to the gas ejection groove 5, and gas is supplied to the gas ejection groove 5 through the gas hole 6. In FIG. 1A, the gas holes 6 are provided so as to penetrate the ceramic dielectric layer 2. However, the gas holes 6 may be provided with gas supply ports on the side surfaces of the ceramic dielectric layer 2. .

FIG. 1B is an enlarged sectional view of the vicinity of the gas ejection groove 5 on the right side of FIG. 1A. According to FIG. 1B, the surface roughness _{Ra (i) of} the mounting surface center region 3a is 0.6 to 0.6.
It is important that the mounting surface outer peripheral region 3b has a surface roughness _{Ra (O)} of 0.7 μm or less, and _{Ra ( O)} is smaller than _{Ra (i)} . By setting _{Ra (i)} to 0.6 to 1.5 [mu] m, the heat transfer of the gas existing in the gap between the wafer and the mounting surface center region 3a causes the mounting surface center region 3a.
, The uniform processing over a wide area of the wafer can be performed in a process such as etching, CVD or sputtering, and a good departure response can be obtained. . In particular, _{Ra (i)} is
It is preferably from 0.7 to 1.2 μm, more preferably from 0.8 to 1 μm, for heat uniformity and detachment response.

If R _{a (i)} is smaller than 0.6 μm, the amount of charge involved in the adsorption increases, and as a result, the adsorbing force for holding the wafer becomes excessively high. When the applied voltage is stopped, it takes a long time to remove a large amount of electric charges, and residual adsorption occurs in which adsorption is maintained. Therefore, desorption response is deteriorated and throughput is reduced. Conversely, when _{Ra (i)} exceeds 1.5 μm,
The gas flow becomes large, the temperature of the wafer fluctuates, and the temperature of the wafer becomes non-uniform.
Defects are likely to occur in processes such as sputtering.

The gas introduced from the gas ejection groove 5 is supplied to the gap between the mounting surface center region 3a and the wafer, and passes through the gap between the mounting surface outer peripheral region 3b and the wafer. Portion, and is discharged out of the electrostatic chuck. However, if _{Ra (O)} is larger than 0.7 μm, gas is likely to be discharged to the outside from a gap between the mounting surface outer peripheral region 3b and the wafer, so that a leak is caused. Since the amount increases and the adsorbing power rapidly decreases, a stable adsorbing power cannot be obtained.

In particular, _{Ra (O)} is preferably 0.6 μm or less, more preferably 0.5 μm or less, in order to attain a high attraction force and to prevent leakage. The lower limit of _{Ra (O)} is not particularly limited, but considering the cost for reducing the surface roughness, 0.05 μm, particularly 0.1 μm, and more preferably 0.2 μm.
μm is preferred.

Further, by making _{Ra (O)} smaller than _{Ra (i)} , the residual suction force can be reduced while maintaining the suction force in the central area 3a of the mounting surface having a large area at a necessary and sufficient strength. it can. In other words, when the surface roughness increases, the surface area involved in the adsorption decreases, and the amount of charge involved in the adsorption force decreases. Therefore, the adsorption force in the central area 3a of the mounting surface becomes smaller than that in the outer peripheral area 3b of the mounting surface. However, if it is set in the above range, it is possible to maintain a sufficient attraction force for performing the treatment.

Further, the surface roughness _{Ra (O)} in the mounting surface outer peripheral region 3b having a small area is made smaller than _{Ra (i)} and the attraction force is increased, so that the mounting surface outer peripheral region 3b can be moved from the mounting surface outer peripheral region 3b to the outside. The amount of gas flowing out to the exhaust gas can be suppressed, and a stable adsorption force can be obtained. When the gas outflow amount increases, the force separating the wafer from the mounting surface outer peripheral region 3b becomes larger than the suction force, and the wafer separates from the mounting surface outer peripheral region 3b,
As a result, the attraction force decreases. In this case, even if R
_{Even if a (O)} and _{Ra (i)} are set to the above values, if _{Ra (O)} is larger than _{Ra (i)} , the mounting surface outer peripheral region 3
The suction force of b decreases, and the suction force of the entire wafer decreases.

Therefore, the surface roughness R of the mounting surface center region 3a
_{a (i)} is set to 0.6 to 1.5 μm, the surface roughness _{Ra (O)} of the mounting surface outer peripheral region 3b is set to 0.7 μm or less, and _{Ra (O)} is set to be smaller than _{Ra (i).} It is important to.

Here, the surface roughness _Ra indicates the average unevenness of the surface. Specifically, the center line average roughness according to Japanese Industrial Standard B0601 is measured by a contact method. For example, using a handy surfing device manufactured by Tokyo Seimitsu Co., Ltd., the center of the groove and the outer periphery of the groove are randomly selected at five points, and the average value of the center line average roughness of at least 20 points is measured.

According to the present invention, it is important that the height of the outer peripheral region 3b of the mounting surface is 0.6 μm or more higher than the height of the central region 3a of the mounting surface. If the height difference is smaller than 0.6 μm, the height difference becomes an error range of the surface roughness, and the effect of providing the height difference is lost. In other words, even if the surface roughness is controlled to improve the thermal uniformity by the gas, if the height difference is less than 0.6 μm, the temperature difference between the electrostatic chuck and the held object surface becomes 30 ° C. or more, and the wafer and ceramic Due to the difference in thermal expansion with the dielectric, the wafer is warped convexly in the outer peripheral direction of the substrate,
The end of the wafer warps, causing gas leak and causing a sharp decrease in the attraction force. This becomes remarkable when the wafer size is large.

Therefore, in FIG. 1 (b), it is necessary that the outer peripheral region 3b described above has a higher horizontal level than the central region 3a described above, and that the height difference d is 0.6 μm or more. The height difference d is 0.6 μm or more, and R
_{Since a (i)} is as large as 0.6 to 1.5 μm, a gap is generated between the wafer and the mounting surface center region 3a, and the temperature of the wafer becomes uniform due to heat conduction of the gas.

Furthermore, since _{Ra (O)} is as small as 0.7 μm or less and the outer peripheral region 3b of the mounting surface is located higher than the central region 3a of the mounting surface, a high suction force is obtained at the outer peripheral portion. Gas leaks can be prevented. as a result,
Uniform and highly reproducible processing can be performed.

Then, the applied voltage was stopped in the central area 3a of the mounting surface because the attractive force of the central area 3a of the mounting surface was smaller than the attractive force of the outer peripheral area 3b of the mounting surface by controlling the surface roughness. Subsequent residual adsorption is unlikely to occur. Even if residual adsorption occurs in the mounting surface outer peripheral region 3b, the area of the mounting surface outer peripheral region 3b is much smaller than the area of the mounting surface central region 3a. High withdrawal responsiveness can be obtained without significantly affecting the sex.

The height difference d depends on the size of the wafer.
In particular, 1 μm or more, further 3 μm or more, more preferably 5 μm
μm or more is preferred. Also, if this height difference d is too large, it becomes equivalent to a large depression in the center,
The wafer may be greatly deformed and cracked, or the vibration of the wafer may increase when the wafer is detached, which may cause a problem of displacement. Therefore, the upper limit of the height difference d depends on the size of the wafer, but is preferably 10 μm or less.

According to the present invention, the mounting surface center region 3
maximum surface roughness R _max of a and placing surface outer peripheral region 3b is 2μ
m or less, particularly preferably 1.5 μm or less, and more preferably 1.2 μm or less. R _max is might locally large scratch or processing defects exceeds 2 [mu] m, causing gas leak in placing surface outer peripheral region 3b.

Further, in the mounting surface center region 3a, R
_{If max} exceeds 2 μm, a large flow of gas flowing locally through a site with a large flaw or processing failure occurs, and the wafer is partially lifted, so that the suction force becomes unstable. Further, since a temperature difference is generated between a portion of the wafer where gas flows and a portion where gas does not flow, variation occurs in processing of the wafer,
The failure rate increases. Therefore, R _max is preferably 2 μm or less.

[0042] Here, the maximum surface roughness R _max denotes the maximum value of surface irregularity. For example, based on the contact method according to Japanese Industrial Standard B0601, using a handy surf device made by Tokyo Seimitsu, etc., randomly select five places of the groove center part and the groove outer part, and measure the maximum height of at least 20 points each. Good.

Further, the distance w from the peripheral end 8 of the mounting surface 3 to the outer periphery 9 of the gas ejection groove is 10 mm or less, particularly 8 mm.
Hereafter, it is more preferably 6 mm or less. The gas introduced into the gas ejection groove 6 passes through the gap between the wafer and the mounting surface outer peripheral region 3b, is released into the processing device provided with the electrostatic chuck, and is removed by the accompanying vacuum device. Is the peripheral end portion 8 of the mounting surface 3, that is, the mounting surface outer peripheral region 3.
The distance from the outermost circumference of b to the outer circumference 9 of the gas ejection groove is 10
mm, and when the gas ejection groove enters the center,
It may be difficult for gas to pass through, and the adsorptive power may be unstable. Also, when w increases, the area of the mounting surface outer peripheral region 3b increases, the suction force of the entire wafer increases, the residual suction force when the applied voltage is stopped increases, and the detachment response tends to deteriorate. There is.

Further, the density of the ceramic dielectric layer 2
Is 98% or more, especially 99% or more, and the maximum pore diameter is 2 μm or less.
Below, it is particularly preferable that it is 1 μm or less. Exists on the surface
Pore size is less than 2μm and exists on the surface
The number of pores is small, so R _{a (O)}And R_{a (i)}Easily small
Compression, maximum surface roughness R_maxShould be controlled to 2 μm or less.
And easier.

The ceramic dielectric layer 2 preferably has a volume resistivity at 50 ° C. of 10 ⁷ to 10 ¹² Ωcm, particularly preferably 10 ⁸ to 10 ¹¹ Ωcm. If the volume resistivity is lower than 10 ⁷ Ωcm, the leakage current from the ceramic dielectric layer 2 to the object to be held increases,
There is a tendency to damage holding objects such as wafers. On the other hand, if the volume resistivity is higher than 10 ¹² Ωcm, the Johnson-Rahbek adsorption force may decrease, and a sufficient adsorption force may not be obtained.

Preferably, the ceramic dielectric layer 2 contains aluminum nitride (AlN) as a main component.
AlN is resistant to corrosion caused by corrosive gas or plasma containing fluorine, chlorine, or the like, can suppress generation of particles, and can prolong product life. In particular, the metal impurities contained in AlN are preferably 2% by weight or less, particularly preferably 1% by weight or less, and more preferably 0.5% by weight or less.

Further, as the metal constituting the electrode 4 of the electrostatic chuck 1 made of aluminum nitride, W, M
o, Pt, Au, Ag, Ni, TiN, WC, W ₂ C,
TiC, TiB ₂ , B ₄ C, or the like can be used. However, when the electrode 4 is formed inside the substrate having the mounting surface 3 (hereinafter referred to as “electrode built-in”), the conductivity and the firing temperature of the ceramics are set. Is high, W, WC, and Mo are preferable. When the electrode 4 is formed on the back surface of the mounting surface 3, any of the above metals may be used.

The relative density of the electrode 4 is preferably at least 90%, especially at least 95%, more preferably at least 97%. As a result, generation of large pores in the electrode 4 can be suppressed, and as a result, the in-plane distribution of the attraction force can be easily made uniform.

FIG. 2 shows another example of the electrostatic chuck of the present invention. The electrostatic chuck 11 of the present invention includes a ceramic dielectric layer 12, a mounting surface 13 provided on the surface of the ceramic dielectric layer 12, and an electrode 14 provided on a surface opposite to the mounting surface 13. Is provided. Although not shown, it goes without saying that a connection line for supplying a voltage to the electrode 14 is included.

The mounting surface 13 is a portion for mounting an object to be held (hereinafter, simply referred to as a wafer) such as a Si wafer.
And a mounting surface outer peripheral region 13b. A gas hole 16 is connected to the gas ejection groove 15,
Gas is supplied through the gas holes 16.

The electrode 14 is formed of the ceramic dielectric 12.
And the base 18, and the ceramic dielectric 12 and the base 18 are integrally formed. There is no problem as long as they are firmly bonded, but it is preferable that the ceramic dielectric 12 and the base 18 are made of the same material in order to reduce residual stress. Therefore, the electrode 14
Is formed in a state buried inside the ceramic. Thus, when the electrode 14 is provided inside,
Corrosion due to plasma generated near the object to be held can be avoided, and there is little danger of disconnection or short circuit.
A highly reliable electrostatic chuck can be realized.

FIG. 3 shows another example of the electrostatic chuck of the present invention, and shows a schematic cross-sectional structure of an electrostatic chuck 21 using a single electrode on a gantry 30. That is, on one surface of the ceramic dielectric layer 22, a mounting surface 23 including a mounting surface central region 23a and a mounting surface outer peripheral region 23b is formed, and an electrode 24 is formed on the other surface. Further, a gas ejection groove 25 is provided on the mounting surface 23, and a gas hole 26 for introducing a gas from outside is connected to the gas ejection groove 25. Further, the above structure
An electrostatic chuck 21 is formed on a surface of a metal gantry 30 by being bonded via an adhesive layer 31.

Although not shown, the electrode 2 is externally provided.
Needless to say, connection wiring for supplying a voltage to 4 is provided. When a voltage is applied between the electrode 24 and the held object 32 such as a wafer on the mounting surface 23,
The held object 32 is electrostatically attracted to the mounting surface 23.

In the case of joining using a brazing material or metal, stress may concentrate on the adhesive layer and cracks or warpage may occur. Therefore, the adhesive layer is preferably an organic adhesive layer. Warpage of the electrostatic chuck 21 can be reduced, gas leakage from the outer periphery can be suppressed, and the attraction force can be increased. In particular, it is preferable that the organic adhesive layer 31 be made of an organic adhesive such as soft silicon, epoxy, or urethane that can reduce the warpage of the held object 32 due to a temperature difference.

FIG. 4 shows another example of the electrostatic chuck of the present invention, and shows a schematic sectional structure of an electrostatic chuck 41 using a plurality of electrodes on a pedestal 50. That is, on one surface of the ceramic dielectric layer 42, a mounting surface 43 composed of a mounting surface central region 43a and a mounting surface outer peripheral region 43b is formed, and a pair of electrodes 4 is formed on the other surface.
4a and 44b are formed.

Further, a gas ejection groove 45 is provided on the mounting surface 43, and a gas hole 46 for introducing a gas from outside is connected to the gas ejection groove 45. Further, the electrode 44
It is integrally formed on the surface of the base 48. In other words, the pair of electrodes 44 is sandwiched between the ceramic dielectric layer 42 and the base 48, and when the ceramic dielectric layer 42 and the base 48 are made of the same material (ceramic), the electrodes are embedded in the ceramic. I have.

The above structure is joined to a metal frame 50 via an adhesive layer 51 to form an electrostatic chuck 41. Although not shown, it goes without saying that connection wiring for supplying a voltage to the electrode 44 from the outside is provided. Then, when a voltage is applied between the electrodes 44a and 44b, the held object 52 such as a wafer on the mounting surface 43 is electrostatically attracted to the mounting surface 43.

In some cases, the processing apparatus is used in a container that generates plasma. In this case, the base (18, 52) is used to generate plasma near the object (32, 52, etc.). 48 or the like is preferably provided with a plasma electrode inside or on the back surface. This greatly contributes to simplification and downsizing of the device structure, and facilitates plasma control.

The electrostatic chuck configured as described above
While maintaining the uniformity and high adsorption power of the substrate, it has the characteristics that it has excellent desorption responsiveness and less gas leakage, and is excellent in all properties of thermal uniformity, adsorption force and desorption responsiveness.
In semiconductor manufacturing processes such as CVD and sputtering,
The present invention can be suitably applied to a process such as carrying a substrate such as a wafer by electrostatic attraction and holding, a transfer, and the like, thereby increasing a throughput.

Next, the method of manufacturing the electrostatic chuck according to the present invention will be described with reference to an example in which the electrostatic chuck shown in FIG. 2 is manufactured using an AlN sintered body as the ceramic dielectric layer.

First, an AlN powder is prepared as a starting material. This AlN powder may be a powder produced by any of the production methods of the reduction nitridation method and the direct nitridation method.
9% or more and an average particle diameter of 3 μm or less are preferable for obtaining a high-purity sintered body. Metal impurities contained in this raw material may be contained in a range that does not affect the adsorption power, but in order to obtain a high-purity sintered body with excellent corrosion resistance,
The content of metals other than Al is preferably 2% by weight or less, particularly 1% by weight or less, and more preferably 0.5% by weight or less.

Since carbon affects the sinterability, it is 1% by weight or less, particularly 0.5% by weight or less, and more preferably 0.3% by weight or less.
The following is preferred. The oxygen content of the sintered body is
It is preferably at most 3% by weight, particularly preferably at most 2% by weight, further preferably at most 1% by weight. Thus, a high-purity sintered body having excellent corrosion resistance can be obtained.

The above aluminum nitride powder is molded,
It has a desired shape with electrodes provided inside. Molding may be performed by a molding method such as die pressing, CIP, tape molding, casting, or the like. The molded body can be calcined, if necessary, after removing necessary binder components at the time of molding.

The electrodes are formed by, for example, preparing a pair of compacts and / or calcined bodies having a relative density difference of 5% or less when the electrodes are built-in, and using a printing method such as metal such as W or Mo on one side. After forming an electrode by applying a paste obtained by mixing a metal compound such as TiN and the main component of the ceramic sintered body, an organic binder, and a solvent, the electrodes may be stacked so as to sandwich the electrodes. As another method, an electrode may be printed on a tape molded body, and after calcining, may be inserted between a pair of pressed calcined bodies.

At this time, it is preferable that the difference in the relative density between the calcined pressed calcined body and the calcined tape formed by the die press and calcined is 10% or less, particularly 5% or less. Thereby, the occurrence of peeling and cracks can be effectively suppressed.

When the electrodes are formed, it is desirable to check the shrinkage after firing in advance and to determine the electrode thickness at the time of formation so that the electrode thickness after sintering is 7 μm or more. For example, depending on the composition, concentration, viscosity and pressing pressure of the electrode forming paste, the electrode thickness is 10 μm or more,
In particular, it is preferable to form it to have a thickness of at least 20 μm, more preferably at least 30 μm.

The flatness of the compact or calcined body to which the electrode paste is applied is preferably 200 μm or less, particularly 100 μm or less, and more preferably 50 μm or less. Thereby, it becomes easy to control the variation of the average distance from the placement surface to the electrode.

Next, the structure composed of the molded body having the electrodes provided therein is fired. Before the firing, the binder component may be removed as required. In addition, baking is a hot press method,
A normal pressure firing method and a gas pressure firing method can be used. In some cases, HIP or heat treatment may be performed.

The sintering will be described by taking a hot press method as an example. First, it is important to load the above structure into a carbon mold of a hot press apparatus, apply a pressure less than the strength of the structure, and then raise the temperature. If pressure is not applied, shrinkage or deformation occurs due to temperature rise. If the pressure is higher than the strength of the structure, the sample is cracked by pressurization, and disconnection or large deformation of the electrode formation portion occurs, which can be prevented.

Next, it is preferable to maintain the temperature at a temperature lower than the firing temperature. This temperature holding step has an effect of making the temperature of the structure uniform, and the holding temperature is preferably 1400 to 1800 ° C., which is close to the shrinkage starting temperature. The pressure during holding is a pressure lower than the strength of the structure, particularly 0.1 to 3 MPa.
It is preferable to set The temperature is preferably maintained for 20 minutes or more, particularly for 1 hour or more, in order to make the temperature of the structure uniform.

After the completion of the temperature holding step, the temperature is raised again, and the pressurizing pressure is set to a pressure higher than the strength of the structure within a temperature range of ± 100 ° C. from the shrinkage starting temperature. This pressure allows one-dimensional contraction to be performed while correcting the deformation of the electrode, thereby keeping the electrode flat. The above-mentioned pressurization start temperature is preferably in a temperature range of ± 50 ° C. from the shrinkage start temperature. It should be noted that pressurization may be performed at the same time when the temperature increase is restarted at the time when the temperature holding is completed.

Here, the shrinkage start temperature indicates the intersection of the extrapolation line of the straight line without contraction and the extrapolation line of the tangent line of the contraction curve in the dimensional contraction curve at a constant heating rate.

Then, firing is performed at a temperature of 2000 to 2250 ° C. to obtain a ceramic sintered body having a built-in electrode. This calcination is preferably carried out at the above-mentioned temperature for at least 20 minutes, particularly at least 1 hour, whereby a dense body can be stably obtained.

Further, it is preferable to apply a pressure higher than the firing pressure after the point at which 90% of the contraction amount of the structure has contracted to further correct the deformation of the electrode. Thereby, the variation in the distance from the surface of the sintered body to the electrode can be further reduced.

The firing pressure is preferably 0.1 MPa or more in order to achieve a relative density of 99% or more. The speed at which the pressure is applied is not particularly limited.

Therefore, for example, an initial pressure of 0.1 to
After applying 0.2 MPa and maintaining the temperature at 1750 ° C. for 1 hour, the temperature was raised again, and a pressure of 0.5 MPa was applied at 1800 ° C.
The firing is performed at 2150 ° C. for 4 hours. After firing, if desired, for example, a pressure of 1 MPa or more may be applied at 2200 ° C. and held for 30 minutes.

In the case where the ceramic sintered body is mainly composed of the aluminum nitride crystal phase, in order to prevent local deformation and a difference in shrinkage due to a portion, or stress deformation due to uneven dispersion of the sintering aid, Al 1% by weight of metals other than
The following is preferred.

The formation of the mounting surface according to the present invention will be described. First, a ceramic substrate having a mounting surface is processed into a desired shape. For example, after forming a gas hole and a gas ejection groove by grinding and drilling, the central area of the mounting surface and the outer peripheral area of the mounting surface are reduced by an average surface roughness _Ra 0.6 to 1 by rotary processing and grinding. Finish to a thickness of 0.5 μm and a maximum surface roughness R _{max of} 2 μm or less. At this time, the height of the mounting surface outer peripheral region is 10 to 100 times higher than the height of the mounting surface central region.
It is preferable to make the height higher by about μm.

Next, the outer peripheral area of the mounting surface is defined as the average surface roughness _Ra.
Finish by rotary or lapping to 0.7 μm or less and maximum surface roughness R _max to 2 μm or less, and adjust the outer peripheral area of the mounting surface to be 0.6 μm or more than the central area of the mounting surface.

Lastly, the substrate after the above-mentioned processing is bonded to the gantry by the organic layer on the side opposite to the mounting surface. For the adhesive layer, a soft resin such as an imide resin, an epoxy resin, a silicone resin, or a phenol resin is used. Also,
In this, a metal or ceramic may be appropriately mixed as a powder or a bulk to increase the adhesive strength. The mounting surface may be processed after bonding.

The processing apparatus of the present invention is suitably used particularly as an apparatus for manufacturing a semiconductor containing a liquid crystal. That is,
In such a manufacturing process, an object to be held such as a wafer is fixed to the mounting surface of the electrostatic chuck of the present invention, and transport, etching, processing such as film formation can be performed efficiently, and productivity is high. A highly reliable semiconductor can be realized at low cost.

[0082]

EXAMPLE An aluminum nitride powder having an average particle diameter of 1 .mu.m by a reduction nitriding method was used as a raw material. If desired, carbon powder having an average particle diameter of 1 μm and Al _{2 having an} average particle diameter of 1 μm may be used.
O ₃ powder was added and mixed so that metals other than Al became 1% by weight or less.

Ethanol and a binder were added to this mixed powder and mixed to obtain a molding powder. This was formed into a disk having a diameter of 300 mm and a thickness of 6 mm by press molding.
Further, it was formed into a shape having a diameter of 80 mm and a thickness of 4 mm as a measurement sample. An electrode was formed using a paste composed of WC, AlN, and an organic binder. A pair of disks were stacked so as to sandwich the electrode, and further pressed, and the formed body was degreased to obtain a structure. This structure was placed in an AlN bowl and fired in a firing furnace. The calcination was carried out in advance at 1750 ° C. near the shrinkage starting temperature for 1 hour, and then calcined at 2150 ° C. for 4 hours.

The maximum pore diameter of the obtained sintered body was determined by polishing the sintered body to a mirror surface state, observing 10 fractured surfaces for each sample by a scanning electron microscope photograph of 1000 times, and measuring the maximum pore diameter. Was measured.

The relative density of the sintered body was determined by first determining the bulk density by the Archimedes method, then grinding the sintered body
It was calculated by comparing with the true density obtained by the He substitution method based on SR1620.

The volume resistivity was measured at 50 ° C. by a three-terminal method based on JIS C2141.

Next, the outer diameter of the sintered body of the disc was processed to 300 mm. Further, gas holes and gas ejection grooves were formed by drilling, and the distance w from the peripheral end of the mounting surface to the outer periphery of the gas ejection grooves was as shown in Table 1.
The entire mounting surface of the mounting surface was previously finished by rotary processing or grinding processing so that _{Ra (i)} and _Rmax shown in Table 1 were obtained. At this time, the height of the mounting surface outer peripheral region from the groove to the outer periphery was higher by about 20 μm than the height of the mounting surface central region from the groove to the center. Thereafter, the outer peripheral area of the mounting surface from the groove to the outer periphery was finished by rotary or lapping so that the average surface roughness _{Ra (O)} and the maximum surface roughness _Rmax became the values shown in Table 1. In addition, the height difference d between the central area of the mounting surface and the outer peripheral area of the mounting surface was adjusted to be the value shown in Table 1.

Then, the aluminum base and the above-mentioned sintered body were joined using an epoxy resin adhesive to produce an electrostatic chuck having a structure shown in FIG.

The thermal uniformity of the substrate is determined in advance by inserting a thermocouple into a surface where plasma is generated at 10 or more locations inside and outside the substrate and a mounting surface near a gas introduction hole. The variation was measured while monitoring the temperature of the mounting surface during gas introduction and gas introduction.

The suction force was required for placing a 1-inch square silicon piece on the mounting surface, applying 500 V (bipolar voltage 250 V) at 50 ° C., and separating the silicon piece from the electrostatic chuck 30 seconds after the application. The force was measured as the adsorption force. Also, after 180 seconds from the voltage application, the application of the voltage is stopped,
The time required for the charge to decrease to 2 KPa or less was measured, and the charge elimination time was defined as a value of the detachment response.

The gas leak was measured by setting the vacuum apparatus to 10 Pa and measuring the flow rate of gas flowing through the groove of the electrostatic chuck with a flow meter. The results are shown in Table 1.

[0092]

[Table 1]

Sample No. of the present invention 2-6, 8-11, 1
In Nos. 3 to 16 and 18 to 33, the adsorption force was as large as 300 MPa or more, the gas leak was 15 sccm or less, the desorption response was 25 sec or less, and the in-plane variation of the substrate was as small as 25 ° C. or less.

On the other hand, a sample N outside the range of the present invention, in which the outer peripheral area of the mounting surface and the central area of the mounting surface have the same height and d is 0, is out of the range of the present invention.
In o.17, the desorption response was as good as 0.5 sec, but the adsorption force was as very low as 80 MPa. The gas leak was as large as 120 sccm.

[0095] The surface roughness R _a is, samples outside the scope of the present invention is the same in mounting surface outer peripheral region and the mounting surface central region N
o. In No. 12, the detachment response was as good as 0.5 sec, but the adsorption force was as small as 150 MPa. Also,
The gas leak was as large as 70 sccm.

Further, the surface roughness R of the outer peripheral area of the mounting surface
_a is outside the range of the surface roughness R _a greater than the present invention of placing surface central region Sample No. Sample No. 1 had a low surface roughness, so the adsorption power was as high as 600 MPa and the gas leak was as small as 0.5 sccm, but the desorption response was as poor as 180 sccm.

Further, the sample No. having a large average surface roughness _Ra of 2 μm in the center area of the mounting surface, which is outside the range of the present invention. 7
Had a good desorption response of 0.5 sec, but a low adsorption power of 200 MPa.

[0098]

As described above, the present invention controls the _Ra of the outer peripheral area of the mounting surface and the center area of the mounting surface, and forms a difference in height on the surface of the mounting surface, so that the heat uniformity of the substrate and the high suction power can be obtained. , And an electrostatic chuck with less detachment response and less gas leak can be realized.

[Brief description of the drawings]

FIG. 1 shows a structure of an electrostatic chuck of the present invention.
(A) is a schematic sectional view, (b) is an enlarged schematic sectional view near the gas ejection groove.

FIG. 2 is a sectional view showing another structure of the electrostatic chuck of the present invention.

FIG. 3 is a sectional view showing still another structure of the electrostatic chuck of the present invention.

FIG. 4 is a sectional view showing still another structure of the electrostatic chuck of the present invention.

[Explanation of symbols]

 1, 11, 21, 41 ... electrostatic chuck 2, 12, 22, 42 ... ceramic dielectric layer 3, 13, 23, 43 ... mounting surface 3a, 13a, 23a, 43a ... Mounting surface central region 3b, 13b, 23b, 43b ... mounting surface outer peripheral region 4, 14, 24, 44a, 44b ... electrode 5, 15, 25, 45 ... gas ejection groove 6, 16, 26, 46 ... gas holes 7, 17 ... bottom of gas ejection groove 8 ... peripheral end of mounting surface 9 ... outer periphery of gas ejection groove 18, 48 ... base 31, 51 ...・ Adhesive layer 32, 52 ・ ・ ・ Object to be held d ・ ・ ・ Difference in height w ・ ・ ・ Width of mounting surface outer peripheral area

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Junji Oe 1-1, Yamashita-cho, Kokubu-shi, Kagoshima Kyocera Co., Ltd. Kagoshima Kokubu Plant (72) Inventor Masaki Terazono 1-1, Yamashita-cho, Kokubu-shi, Kagoshima Kyocera Inside the Kagoshima Kokubu Plant (72) Inventor Yasushi Yasuda 1-1, Yamashita-cho, Kokubu-shi, Kagoshima Prefecture Kyocera Corporation Kagoshima Kokubu Plant (72) Inventor Hitoshi Ata No. 1-1 Yamashita-cho, Kokubu City, Kagoshima Prefecture Kyocera Corporation Kagoshima Kokubu Plant F-term (reference) 3C007 AS24 DS01 FS10 NS13 5F031 CA02 HA02 HA16 HA40 MA28 MA29 MA32

Claims (7)

[Claims] 1. A ceramic dielectric layer, a mounting surface provided on a surface of the ceramic dielectric layer for holding an object to be held, and provided so as to face a surface opposite to the mounting surface. An electrostatic chuck comprising:
The mounting surface is separated into a mounting surface outer peripheral region and a mounting surface center region by a gas ejection groove, and the surface roughness _Ra is 0.6 to 1.5 μm in the mounting surface center region. The outer peripheral area of the mounting surface is 0.7 μm or less, the surface roughness of the outer peripheral area of the mounting surface is smaller than the surface roughness of the central area of the mounting surface, and the height of the outer peripheral area of the mounting surface is higher than the above. An electrostatic chuck characterized in that the height is at least 0.6 μm higher than the height of the placement surface center region. 2. A maximum surface roughness R _{ma x} of the mounting surface outer peripheral region and the mounting surface central region, the electrostatic chuck of claim 1, wherein a is 2μm or less. 3. The electrostatic chuck according to claim 1, wherein a distance from a peripheral end of the mounting surface to an outer periphery of the gas ejection groove is 10 mm or less. 4. The electrostatic chuck according to claim 1, wherein said ceramic dielectric layer has a density of 98% or more and a maximum pore diameter of 2 μm or less. 5. The electrostatic chuck according to any one of claims 1 to 4, wherein the volume specific resistance of 50 ° C. of the ceramic dielectric layer is 10 ⁷ ~10 ^{1 2} Ωcm. 6. The electrostatic chuck according to claim 1, wherein said ceramic dielectric layer contains aluminum nitride as a main component. 7. A processing apparatus comprising the electrostatic chuck according to claim 1 for holding an object to be held.